arXiv subjects

Masao Ninomiya

Publications and source records attributed to Masao Ninomiya.

42 records · Page 3Linked to original sources

arXiv2003

Limiting Temperature, Limiting Curvature and the Cyclic Universe

We propose a new type of cosmological model in which it is postulated that not only the temperature but also the curvature is limited by the mass scale of the Hagedorn temperature. We find that the big bang of this universe is smoothly connected to the big crunch of the previous universe through a Hagedorn universe, in which the temperature and curvature remain very close to their limiting values. In this way, we obtain the picture of a cyclic universe. By estimating the entropy gained in each big crunch and big bang, we reach the conclusion that our universe has repeated this process about forty times after it was created at the Planck scale. We also show that the model gives a scale-invariant spectrum of curvature perturbations.

hep-th↗

arXiv2001

A New Type of String Field Theory

We propose a new way of second quantizing string theory. The method is based on considering the Fock space of strings described by constituents which make up the $X^μ_R$ and the $X^μ_L$ i.e. the right and left mover modes separately. A state with any number of strings get represented by the Cartesian product of two free particle Fock spaces, one for right mover degrees of freedom, and one for left. The resulting string field theory is a free theory.

hep-th↗

arXiv1998

Dirac Sea for Bosons

It is proposed to make formulation of second quantizing a bosonic theory by generalizing the method of filling the Dirac negative energy sea for fermions. We interpret that the correct vacuum for the bosonic theory is obtained by adding minus one boson to each single particle negative energy states while the positive energy states are empty. The boson states are divided into two sectors ; the usual positive sector with positive and zero numbers of bosons and the negative sector with negative numbers of bosons. Once it comes into the negative sector it cannot return to the usual positive sector by ordinary interaction due to a barrier. It is suggested to use as a playround models in which the filling of empty fermion Dirac sea and the removal of boson from the negative energy states are not yet performed. We put forward such a naive vacuum world and propose a CPT-like theorem for it.We study it in detail and give a proof for $λ/4 (ϕ^+ϕ)^2$ theory. The CPT-like theorem is a strong reflection, but does not include inversion of operator order which is involved in the ordinary CPT theorem. Instead it needs certain analytic continuation of the multiple wave function when the state is formulated as a finite number of particles present.

hep-th↗

arXiv1995

Scaling Behavior of Ricci Curvature at Short Distance near Two Dimensions

We study the renormalization of the Ricci curvature as an example of generally covariant operators in quantum gravity near two dimensions. We find that it scales with a definite scaling dimension at short distance. The Ricci curvature singularity at the big bang can be viewed as such a scaling phenomenon. The problem of the spacetime singularity may be resolved by the scale invariance of the spacetime at short distance.

hep-th↗

arXiv1993

Ultraviolet Stable Fixed Point and Scaling Relations in 2+$ε$ Dimensional Quantum Gravity

We formulate a renormalizable quantum gravity in $2+ε$ dimensions by generalizing the nonlinear sigma model approach to string theory. We find that the theory possesses the ultraviolet stable fixed point if the central charge of the matter sector is in the range $0~<~c~<~25$. This may imply the existence of consistent quantum gravity theory in 3 and 4 dimensions. We compute the scaling dimensions of the relevant operators in the theory at the ultraviolet fixed point. We obtain a scaling relation between the cosmological constant and the gravitational constant, which is crucial for searching for the continuum limit in the constructive approach to quantum gravity.

hep-th↗

arXiv1992

Scaling Exponents in Quantum Gravity near Two Dimensions

We formulate quantum gravity in $2+ε$ dimensions in such a way that the conformal mode is explicitly separated. The dynamics of the conformal mode is understood in terms of the oversubtraction due to the one loop counter term. The renormalization of the gravitational dressed operators is studied and their anomalous dimensions are computed. The exact scaling exponents of the 2 dimensional quantum gravity are reproduced in the strong coupling regime when we take $ε\rightarrow0$ limit. The theory possesses the ultraviolet fixed point as long as the central charge $c<25$, which separates weak and strong coupling phases. The weak coupling phase may represent the same universality class with our Universe in the sense that it contains massless gravitons if we extrapolate $ε$ up to 2.

hep-th↗